I have used them...honestly, don't waste your money. You would be better off putting the investment into a new pair of studded boots. I have used Chota Citicos with the screw in studs for their felt for 4 years now...They have been great. One thing I forgot to mention...removable if you are fishing from a drift boat.
Or..I have not tried this but others have. Take the boot to a shoe repair man with the new felt and have them repair it.